<p>kinetic energy is not conserved because if you calculate total KE after and total KE before you will find that there is less aftewrads</p>
<p>For the length one, you have to find the correct voltage due to internal resistance. I posted what you do...V = emf - Ir, V = 12, not 16.</p>
<p>it was 4.0 N, not 100 N</p>
<p>4.0 N = (80 N/m) * x</p>
<p>and it should be in meters, not in newtons (x is distance stretched)</p>
<p>Does anyone know when CB posts the official answer thing up?</p>
<p>Sometime in July/August.</p>
<p>Damn. I totally blew #2. If forgot to use F = ma!! I knew I'd blank during the test...</p>
<p>Concerning the force acting on the mass of the entire system...
Just some thoughts here, Im not declaring anything because Im not sure. The prompt said that both blocks had the same acceleration. So shouldn't you do a=F/m for the 8 kg block, because you know the force on that one and the mass, and then do F=ma for the other block because you know its mass and the acceleration? That's what I was thinking. If you used the mass of the entire system, wouldn't you get the same force for both blocks? And if that was the case, what would be the point of the question asking you to "calculate" the force on the second block?</p>
<p>So we get the guidelines AFTER we get our scores?</p>
<p>no, you wouldn't do the F = ma on just the 8 kg block.. this is because the force is acting on the 8kg block AND the 2kg block (they are attached together by the spring, so they will move together when a force is applied.. the spring will stretch for a time, but the force will eventually overcome the stretch and begin to move the 2 kg block with the 8 kg block).. there is a tension created in the spring that will cause the 2 kg block to have the same acceleration as the 8 kg block, but the overall force indicated applies to the entire system</p>
<p>my physics teacher explained me this and showed me a test from a few years ago that had a problem similar to this one.. and that's how it works</p>
<p>i thought the same thing you did, roz707, when i took the test (and did that too), but after you think about it for a little while (and have your physics teacher explain it to me like mine did), then what i've listed above is right</p>
<p>anyone mind explaining how to do each part of the released test?</p>